A forest is a region with a high thickness of trees. There are lots of definitions of a forest, based on a variety of criteria. These plant communities cover large areas of the world and function as animal habitats, hydrologic flow modulators, and soil conservers, comprise one of the most main aspects of the Earth's biosphere. Although often thought of as carbon dioxide sinks, mature forests are about carbon neutral with only disturbed and young forests acting as carbon sinks. However mature forests do play an important role in the global carbon cycle as stable carbon pools, and clearance of forests leads to an increase of atmospheric carbon dioxide levels.
Forests can be found in all regions talented of sustaining tree growth, at altitudes capable of the tree-line, except where natural fire frequency is too high, or where the surroundings has been impaired by natural processes or by human activities.